The present invention relates generally to hearing testing probes placed within ear canals that are coupled to an instrument that monitors the condition within the ears. More specifically, the present invention provides a hearing testing probe with integrated sensor(s) configured to measure environmental conditions. The present invention further provides a hearing testing probe with integrated heating element(s) configured to provide active temperature control.
Hearing test devices that monitor the condition within a human ear are known. Such test devices generally require that the person performing the test (the “operator”) place a test probe of the device within the ear canal of a test subject. Once the probe is placed properly within the ear canal, the operator activates the device, usually by pressing a button or the like. The device then emits test signals into the subject's ear through the probe in the ear canal. In response to the test signals emitted, the device receives response signals from the ear, likewise through the probe in the ear canal. Such response signals received are then used to determine whether the ear is functioning properly.
Audiological testing for hearing impairment commonly requires an acoustic, air pressure, and/or vibratory stimulus to be presented to the test subject. Several of the methods for hearing evaluation require the use of a probe to generate and couple the stimulus directly to the subject's ear canal. Examples of hearing tests using these probes include optoacoustic emissions, acoustic immittance, acoustic reflex, reflectance, and, in some cases, auditory brainstem response. For each of these tests, certain characteristics of the stimulations need to be applied accurately in order to provide an accurate evaluation of the results.
In order to provide an accurate evaluation of the results, frequency response, magnitude, distortion, and other characteristics of the stimulus should be presented appropriately and measured accurately. However, environmental conditions, such as varying humidity levels, temperatures, and barometric pressures, for example, typically found in human ear canals can cause performance changes in microphone and speaker components commonly used in hearing testing probes.
An exemplary problem encountered when using existing hearing probes is the stability of the pressure response relative to the environmental humidity. The materials typically used in the diaphragms of certain types of microphones are hydroscopic, causing a shift in pressure sensitivity corresponding to changes in humidity. The change in sensitivity is often in the range of 0.02 to 0.06 dB per percent change in humidity. The change in sensitivity creates a difference between the calibrated and measured acoustic levels indicated by the microphone. This error adds a degree of uncertainty to the measurements.
Another problem encountered when using existing hearing probes is the risk of condensation on the internal components of the transducer(s). The high humidity levels commonly found in the ear canal can cause condensation to develop on the colder probe elements. This condensation may cause minerals or dirt to be irrecoverably deposited and cause a permanent and degrading change in performance of the transducer.
Barometric pressure at a given location typically changes no more than 3% from day to day. However, a system calibrated at one altitude and then put into service at a location of a different altitude may not provide the intended or indicated stimulus or measurement. The barometric pressure difference between sea level and a high-altitude location, such as La Paz, Columbia at roughly 12,000 ft. above sea level, can result in an apparent increase in the volume of the ear canal, as measured by the probe, by as much as 60%. This apparent change in volume could cause a 4 dB reduction in stimulus and measurement levels if a correction is not applied.
Hearing tests commonly rely on the coupling of stimulus into the inner ear, and some hearing tests also require a measurement of corresponding emissions from the ear to make proper diagnostic determinations. A seal to the ear canal is typically desired or required to properly perform the test function. During the insertion of the eartip to the ear canal, the air in the ear canal may be compressed. This pressure differential may cause a shift in the apparent stiffness of the tympanic membrane, causing a change in the conduction of the stimulus and emissions from the middle ear to the ear canal, adversely affecting the accuracy of the hearing test.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application.